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Can
Human Cloning be Made Safe?
Saturday, 01 November 2003
"There are continued claims of attempts to
clone humans using nuclear transfer, despite the serious problems that have
been encountered in cloning other mammals. It is known that epigenetic and
genetic mechanisms are involved in clone failure, but we still do not know
exactly how. Human reproductive cloning is unethical, but the production of
cells from cloned embryos could offer many potential benefits. So, can
human cloning be made safe?"
— from Nature Reviews Genetics.
Writing in the journal Nature
Reviews Genetics, a group of Scottish scientists say the biological
process behind cloning needs to be better understood to make it more
efficient and it needs to be more systematically investigated if potential
treatments for diseases are to be delivered by therapeutic cloning.
The experts, who include Ian Wilmut of Scotland's Roslin Institute and one of the
creators of Dolly the Sheep, believe cloning research so far has been done
in a very random way.
The plans for therapeutic cloning should even be shelved until more is
known about how cloning works – and why it fails so often.
"There are a lot of questions to ask about cloned cells before you
can justify putting them in a patient," he told New Scientist.
"Normally during fertilisation you have an egg and a sperm coming
together and their genetic information is packed in special ways for the
egg and for the sperm," he explained in an interview with the BBC.
"What we do is take out the genetic information from the egg and
put in the genetic information from a cell which is packed in a completely
different set of proteins."
"What that egg has to do is struggle to reassemble that genetic
information in a way in which it can control normal development."
Wilmut and his colleagues argue that the only way to answer those questions
is to thoroughly dissect the failures of animal cloning, rather than
continue to celebrate its successes. Wilmut says cloner’s need to
systematically study every aspect of the cloning process, its genetic and
physiological effects on embryo, placenta, foetus and live animal.
Proponents of human cloning argue that embryo selection on the basis of the
screening of embryos would allow only those that passed this 'safety
test' to progress in the developmental process; for example, cells
could be removed both at the pre- and post-implantation stages and assessed
for imprinting errors and gene expression. However, reliable
preimplantation selection is impossible at present, given that it would
require knowledge of all of the potential adverse epigenetic effects.
To accurately assess the issue of cloning safety, geneticists,
developmental biologists and pathologists must work together to dissect the
underlying mechanisms, with the ultimate aim of producing an integrated
view of the main 'check points' in the procedure and how the
modification of techniques can be developed to reduce what is, at present,
an unacceptable level of clone failure.
They conclude the article by saying: "Our experience with other
mammals shows us that any attempts at cloning humans are inherently unsafe
at present. On these grounds alone, scientists should not condone human
reproductive cloning, even without taking into account the equally
important ethical and moral issues."
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